Frequency changing system



June 17, 1941. J.'A. RADO FREQUENCY CHANGING SYSTEM Filed Dec. s, 1939INVENTOR JOHN A.RADO

ATTORNEY Patented June 17, 1941 FREQENCY onANGiNo SYSTEM John'A.'jRa'do,Flushing, N. Y., assignor to HazeltineCorporation; a corporation ofDelaware Appliance VDecember 30,1929, serial' No'. 311,901

6 Clainis (CL "Z50-0) .cause the reactive current flowing in thecontroltube anode circuit `incidentally to depart lfrom the desired90-degree phase with respect to the This invention relates tofrequency-changing systems and particularly to Aautomatic.frequencycontrol for suchsystems embodied in modulatedcarrier signal receivers ofthe superheterodyne type, especially television receivers. s

Superheterodyne receivers provided Witha fre-lv quency-changingsystemfor selecting predetermined Inodulated-carrier `signalsand derivingtherefrom intermediate-frequency modulated signals are well known. f`Such frequency-chang, ing systems oftenare .provided with automaticfrequency control means .including a correction circuit coupled to. theoscillator` circuit of the frequency-changing means kfor varyingtheleective reactance thereof to maintain .the'frequency of theoscillator circuit atthe proper value necessary for deriving theselected intermediate-frequency signals. One system of controlling-theoscillator frequency involves a control tuloeik the anode circuit ofAwhchisin parallel withthe oscillator-tuned circuit. andthe controlelectrode of which is excited voy a potential which has, by means of asuitable phasing network, been shifted 90 degrees with respect/to thevoltage across the tuned circuit of the oscillator sothat the. componentof. current which is common to the control-tube anode and lthetunedcircuit is 90 degrees out ofphase with the voltageacross. this tunedcircuit. The controlJtube/thussimulates a reactance in parallel.with-the oscillator-tuned circuit. The magnitudey of this reactance andhence the oscillatork frequency, is determined by the mutual conductanceof thev control tube, which, in turn, is controlled by the bias yvoltagedeveloped and fed to the vcontrol-tube'grid return oy airequency/.discriminator or detector. In this WayVtheJlOCal oscillatorfrequency is shifted in a directionV that tends toreduce-the differencebetween` the intermediate frequency developed and the mean frequency tovwhichI the intermediate-frequency selector circuits are tuned. l

While the operation-ofsuchautomatic frequency conjtrol` systemsis-satisfactory''forthe conventional reception of modulatcrd-carriersigf nais in the broadcast bandv of frequencies; it is oftenunsatisfactory for the vreception of modulated-carrier Vsignals ofultra-high frequencies, for example, in the frequency range assigned totelevision, because Vvelectronv transit time Veffects aresuicient toaffect Athe operation 'of -both the oscillator and control tube,Which-efiects interfere with the normal `operation :of fthe system whenthe receiver yis tuned from fone#ultra-high 4 frequencyto.another.-Suchtransitfltimerefiects oscillator voltage `as theoscillator-tuned circuit is tunedto diiferent frequencies in theultra-highfrequency range.

It is an object of the present invention, therefore, to provideanimproved frequency-changing system for a modulated-carrier signalreceiver of the superheterodyne type which overcomes the above-mentioneddiiilculties anddisadvantages of such arrangements of the prior art.

It is a more specific object of the invention to provide an improvedautomatic frequency control system fortelevision signal receivers of thesuperheterodyne type.

In accordance with v.this invention, there is providedin anultra-high-frequency modulatedcarrier signal receiver aYfrequency-changing system for deriving from selected receivedmodulated-carrier signals intermediate-frequency y modulated-carrier,signals,-Which comprises an oscillator circuit, means for selectivelyproporv tioning` the constants of the oscillator circuit to oscillateYat any ydesired one of a plurality of different frequencies, anda'frequency-correction circuit coupled to .theoscillator circuitincluding electron-discharge variableimpedance means to ladjust thefrequency of the oscillator'circuit to the proper value necessary forvderiving the selected intermediatef'frequency signals.A In afrequency-.changingsystem of this kind, the phase sangle of fthevariableimpedance means control- .,'correctionei the oscillator.

ling Y,the oscillator frequencyincidentally tends tovary withrespectptothe oscillator circuit voltage with variations in frequencydue to variations vinthe effectief Ielectron transit time lofthe-impedance; means, thereby to/impair Ythe frequency To counteract anytendency of` the phase angle'of such variable impedanceineans to varywith variations in fre- .quency resulting from the selectionof any de-Ysiredone.: of ilthelplurality of different oscillator Y. portioning theconstants'of the compensating circuit lto counteractfany tendencyof thephase angle ofV such variable impedancenieans to vary with variations infrequency. The invention also comprisesunicontrol means :forsimultaneously operating the means for selecting Vthe constants oftheoscillating' and compensating circuits,

-' `whereby any tendency inthe frequency-correo- -tion circuit towardundesired phase anglevariavention, together With other and furtherobjects thereof, reference is had to the following description taken inconnection with the accompanying drawing, and its scope will be pointedout in the appended claims.

In the accompanying drawing the single figure is a circuit diagram,partly schematic, of a complete superheterodyne receiver embodying the Ypresent invention.

Referring now more particularly to the drawing, there is shownschematically a receiver of the superheterodyne type including anantenna system l, I connected to a radio-frequency amplifier II, towhich is connected in cascade, in the order named, a frequency-changingsystem including a modulator I2 to which is coupled by condenser 56 alocal oscillator 24, an intermediate-frequency amplifier I3, and avideo-signal channel comprising a video-intermediate-frequency amplierI4, a detector I5, a Video-frequency ampler It, and an image-reproducingdevice I'I. Also coupled in cascade with the intermediate-frequencyamplier I3 is a soundsignal channel comprising, in the order named, asound-intermedate-frequency amplifier I8, a detector I 9, anaudio-frequency amplifier 20, and a sound-reproducing device 2 I. Theelements or components III-2|, inclusive, all may be of conventionalwell-known construction so that a detailed illustration and descriptionthereof is deemed unnecessary herein. A frequency discriminator |9a, ofany suitable or conventional type, is coupled to the soundintermediate-frequency amplifier |8 and its bias output applied to theoscillator24 over a conductor |913, as described in detail hereinafter.

Neglecting for the moment the particular operation of thefrequency-changing system embodying the present invention, the systemabove-described includes the features of a conventional superheterodynetelevision receiver. The operation of such a receiver being Wellunderstood in the art, detailed explanation thereof is deemedunnecessary. In brief, however, the tunable circuits of theradio-frequency amplifier I I and frequency changer lil- 24, areadjusted to select the desired modulated-carrier signals intercepted bythe antenna system III, II) and to convert them tointermediate-frequency signals. These signals are selected and ampliedby the intermediatefrequency amplifier I3 and translated therefrom tothe video intermediate-frequency amplifier I4 and to thesound-intermediate-frequency amplier I8. In the video-signal channel ofthe receiver the video-intermediate-frequency signals are translated tothe detector l5 wherein the video-frequency modulation components arederived. These video-frequency components are amplified in thevideo-frequency amplifier I6 and reproduced by the image-reproducingdevice Il in a conventional manner. The sound-frequency modulationcomponents are derived by the detector I9 and amplified by theaudio-frequency nals being reproduced by the loudspeaker 2| in aconventional manner.

Referring now more particularly to the parts of the frequency-changingsystem comprising the present invention, the oscillator system 24comprises an oscillator tube 23 and a control tube 22, both of thepentode type. The oscillator, per se, is a. conventional Colpittsoscillator, a type at present commonly used in television receivers. Theoscillator is provided with means for selectively proportioning theconstants of the oscillator circuit to oscillate at any desired one of aplurality of different frequencies comprising a frequency-determiningcircuit comprising including a selector switch 25 for selectivelyincluding one of a plurality of fixed inductances 26, 2l, 28 in thecircuit, each being tuned by inherent circuit capacitance indicatedconventionally by dotted-line condenser 29. The capacitance 29 comprisesthe inherent capacitance of the inductance element in circuit, Wiringcapacitance, and tube interelectrode capacitances. In order to developan oscillator circuit voltage, one terminal of suchfrequency-determining circuit is connected directly to the screen of theoscillator tube 23, acting as an anode, and to the cathode through acoupling condenserv30. The grid of the oscillator tube 23 is connectedto the other terminal of the frequencydetermining circuit through a gridleak 3| and condenser 32 and a by-pass condenser 33. The suppressor gridof the tube 23 is grounded, While the cathode is grounded. for directcurrent through a radio-frequency choke 35. Condenser SII, inconjunction with the inherent cathode-toground capacitance 30a of tube23, form the capacitance divider required by the Colpitts circuit.

The frequency-changing system is provided with a frequency-correctioncircuit coupled to the oscillator circuit v including electron-dischargevariable impedance means, comprising the control tube 22, connected tosimulate a variable impedance to adjust the frequency of the oscillatorcircuit to the proper value for derivingl the selectedintermediate-frequency signals. Speciiically, the plate. of the tube 23.is connected by a blocking condenser 36 to the control grid of thecontrol tube 22the anode circuit of this tube being connected directlyacross the .frequency-determininghcircuit, as indicated. The plate ofthe tube 23 is used here merely as a coupling device. The cathodecircuit of the control .tube 22 includes undesired but inherent cathodelead inductance 31 and a conventional biasing circuit 33. As willbeexplained hereinafter in greater detail, the phase angles of theimpedance means comprising tube 22 and of the oscillator vacuum tube 23incidentally tend to vary with respect to the oscillator circuit voltageWitlr variations infrequency due to variations in the effect of electrontransit time of vrthe vacuum tubes, thereby to impair the frequencycorrection of the oscillator. Io avoid such variations of the phaseangles of these tubes with frequency, the frequency-changing systemincludes an oscillator voltage compensating circuit comprising aplurality of compensating resistors 39, 40 and 4I. This compensatingcircuit is coupled to the frequency-correction circuit; specifically,space current is supplied from a source, indicated at -I-B, to theanodes and screens of tubes 22 and 23 through one of the resistors 35,

Y 40 and 4|. The frequency-changing system adamplier 2li, the amplifiedaudio-frequency sig- 75 ditionally includes means for selectivelyproportioning the constants of the compensating circuit to counteractany tendency of the phase angles of the :impedance means and of theoscillator vacuum tube to vary with frequency resulting'from`ftrol-'bias"voltage changes' the frequency 'of "the the'selectionofanydesired one of theplurality of different oscillator frequencies, thismeans comprising a 'selector switch 42' which is arranged selectively toconnect the anode circuits of tubes 22and'23-through one of theresistors 39, 40 and lll to the space current source +B. The platecircuit of the tube 23 includes a resistor 43 which, with the inherentinput capacitance ofthe control tube 22 'and output capacitance of tube23, represented by the dotted-line condenser 44 and hereinafter referredto as input capacitance of tube 22, comprises a phase-shifting impedancefor applying tothe control grid of tube 22 a Voltage somewhat less than90 degrees displaced in phase from that across the frequency-determiningcircuit of the oscillator. The automatic frequency control bias voltagefrom the frequency discrim- Y inator |901. is applied by conductorleb-to the control grid of the control tube 22 to determine itstransconductance. VThe selector switches 25 and 42 are connected forsimultaneous operation by a unicontrol mechanism, conventionally shownby the dashed line 45.

The value of resistor 43 is so chosen in relation to the values ofeffective tube transadmittances and the input capacitance 44 of tube 22that the output current of tube 22 is 90 degrees out of phase with theoscillator voltage at a given frequency.l At the oscillator frequenciesrequired in receiving television signals there is an appreciabletransadmittance angle between the voltage applied to the controlelectrode of tube 22 and the current output thereof and'between thevoltage developed at the screen of tube 23 and the anode current thereofwhich is a function of frequency and of the operatingA voltages. The`values of the resistors 39,' 4Q, and 4I are, therefore, chosen to soalter the operating voltages of tubes 22 and 23 as to maintain theresultant phase angle between the oscillator voltage and reactivecurrent output of tube 22 at 9b degrees for each selected oscillatorfrequency.

These oscillations are applied to the modulator f l2 through Vthecondenser 45. This causes the modulator l2 to produce the desiredintermediate-frequency modulated-carrier signal. Any slight variation ofthe intermediate frequency supplied to the frequency discriminatorlila., due to drifting or Inistuning of the oscillator, causes thediscriminator `I 9a to develop a corrective control-bias Voltage whichis applied to the control electrode of control tube 22 over conductor|919 to vary the transconductance Yof tube 22. Since the anode circuitof the control tube 22 is in parallel with the frequency-determiningcircuit of the oscillator tube 23 and its anode current, which iseffectively a control current supplied to the frequency-determiningcircuit, is 90 degrees out of phase with the voltage across theoscillator circuit, the control tube simulates a variable re- Y actanceacross the frequency-determining circuit.

As aresult', a change of transconductance of the tube 22 produced bytheautomatic frequency con-v 's'cillatorto maintain the intermediatefrequency at itsA desiredv mean value. Howeverfas :stated above, inchanging from one oscillator frequency to 'another'by means of switch25,there is an incidental tendency accompanying these shifts in frequencyfor the current in the correction circuit to vary in phase with respectto the oscillator circuit voltage.

The factors determining the magnitude of the phase angle of the currentoutput of tube 22 with respect to oscillator voltage are:

1. The phase angle at the oscillator'frequency of the impedance ofresistor 43 and input capacitance 44 in parallel.

2. The phase angle of theV cathode-to-ground impedance of control tube22.

3. The transadmittance angles from control electrode to anode of controltube 22 and from screen to anode of oscillator tube 23.

The above three quantities are aifected in magnitude by variation ofoscillator frequency; in addition, the magnitude of the twotransadmittance angles may be varied over a considerable range byvarying the unidirectional potentials applied to anode and screen.

In accordance with this invention, the uni* directional voltages appliedto the anodes and screens of the tubes 23 and 22 are controlled by meansof the selector switch 42 to compensate for the tendency of the otherfactors to change the phase angle of the control-tube current withvariation of the selected oscillator frequency.

A specific example will illustrate the operation to be expected in thesystem of this invention. Let it be assumed, for example, that selectorswitch 25 connects the tuning inductance 2li into thefrequency-determining circuit of the oscillatorl andthat the voltagefromsource +B is applied to the anodes and screens of tubes 22 and 23through resistor 39 by switch 42 and that oscillation commences at thedesired frequency. Neglecting for the moment electron 'transit timeeffects in the vacuum tubes 22 and 23 and all circuit impedances exceptcapacitance 44, a current inphase with the oscillator voltage ows incapacitance 44 and a voltage appears at the control electrode of tube 22which lags the oscillator voltage by degrees. The resulting anodecurrent of tube `22 is at the proper QO-degree phase angle with respectto `the oscillator Voltage. However, if electron transit time in tube 23be considered, it causes the plate current of tube 23 to lag somewhatbehind'the oscillator voltage and likewise, for the same reason, theanode current in control tube-22 lags behind its control electrodevoltage. liurtlfiermore, V Vcathode-to-ground yimpedanceofstube22,particulariy lead inductance 3l, increasesY this-lag. Thenecessary correction for this set ofconditions can be made by canceilingsome of the effect of the reactance of capacitance '44 by-means ofresistor'43 in the anode circuit of tube 23.

Butnow should switch Y25 be operated to select another tuninginductance, for example, inductance 21, to develop another oscillatorfrequency which is higher than the oscillator frequency produced by thetuning inductance 26, the electron transit time, while of the sameabsolute Value, is now a larger fraction of the period of the generated'wave so that thephase shift of the output current of oscillator tube' 23and of the anode current of the control tube 22 with respect to theoscillator voltage is increased. At 4the same time, resistor -43Yis nowof -tooihigh a value to vcancel the required portion of the phase shiftdue to capacitance 44, which is lower in reactance at the higherfrequency. However, in accordance with the present invention, both thesevariations in phase angle are compensated for by the simultaneousselection by means of simultaneous voperation of the switch 42 With theswitch 25, Ofanother operating voltage of suiciently higher value toshorten the electron transit times in both vacuum tubes and therebytoreduce the transadrnittance angles therein, thus restoring the proper90-degree phasebetween the anode current of tube 22 and the oscillatorvoltage.

The fiXed-inductance elements 26, 21, and 28 are selectivelyproportioned to cause the oscillator circuit to oscillate at any desiredone of three differ-ent frequencies. The fixed compensating resistors39, 40, and 4| likewise are selectively proportioned so that the voltageapplied by the compensating circuit to control the electron transittimes of the vacuum tubes 22 and 23 counteracts any tendency of thecontrol current supplied to the oscillator-tuned circuit by the vacuumtube 22 in the correction circuit to vary in phase with respect to theoscillator circuit voltage by virtue of variations in frequencyresulting from the selection of any desired one of the three differentoscillator frequencies. Thus, the unicontrol means 45 operates theswitches 25 and 42 simultaneously to select the constants of theoscillating and compensating circuits s that any tendency towardvariation in phase of the. control current resulting from the selectionof a desired oscillator frequency is minimized.

The following values have been found satisfactory in the design of afrequency-changing system according to the present invention:

Video-intermediate frequency megacycles 12. 75 Sound-intermediatefrequency do 8. 25 Radio-frequency band range (l) do 44-50Radio-frequency band range (2) do 50-56 Radio-frequency band range (3)do 66-72 Oscillator frequency (1) do 5S Oscillator frequency (2) do 64Oscillator frequency (3) do 80 Inductance 26` microhenries 0.20Inductance 27 do 0. l5 Inductance 28 do 0. 10 Inductance 37 do 2.00Resistor 39 ohms 5, 000 Resistor 40 do 2, 500 Resistor 41 do 1, 000Resistor 43 do 15G-200 Capacitance 29 micro-microfarads 30 Capacitance44 d0 20 Control tube 22 6AC'7 Oscillator tube 23 GAC? Voltage source +Bvolts 250-300 A. F. C. Control-bias voltage range volts 2-6 Phase shiftdue to electron transit time at U megacycles degrees 35-40 While therehas been described what is at present considered to be the preferredembodiment of this invention, it will be obvious tothose skilled in theart that various changes and modifications may be made therein Withoutdeparting from the invention, and it is, therefore, aimed in theappended claims to cover al1 such changes and modifications as fallwithin the true spirit and scope of the invention. Y

What is claimed is:

carrier signal receiver, a frequency-changing system for deriving fromselected received modu- 1. In an ultra-high-frequencymodulatedlated-carrier signals intermediate-frequency modulated-carrier,signals comprising, an oscillator circuit, means .for selectivelyproportioning the constants of said oscillator circuit to oscillate atany desired one of a plurality of different frequencies, afrequencyecorrection circuit coupled to said'oscillator circuitincluding electron-discharge variable impedance means to adjust thefrequency of said oscillator circuit to the proper value for derivingthe selected intermediate-frequency signals, the phase angle of. saidimpedance incidentally tending to vary with respect to the oscillatorcircuit voltage ,with variations in frequency due to variations in theeffect of electron transit time of said impedance means thereby toimpair the frequency correction of said oscillator, an oscillatorvoltage compensating circuit coupled to said correction circuit, andmeans for selectively proportioning the constants of said compensatingcircuit to counteract any tendency of the phase angle of said impedanceto vary with frequency resulting from the selection of any desired oneof said plurality of different frequencies.

2. In an ultra-high-frequency modulated-carrier signal receiver, afrequency-changing system for deriving from selected received modulatedcarrier signals intermediate frequency modulated-carrier signalscomprising, an oscillator circuit, means for selectively proportioningthe constants of said oscillator circuit to Oscillate at any desired oneof a plurality of different frequencies, a frequency-correction circuitcoupled to said oscillator circuit including electron-discharge variableimpedance meansto adjust the frequency of said oscillator circuit to theproper value for deriving the selected intermediate-frequency signals,the phase angle of lsaid impedance incidentally tending to Vary withfrequency due to variations in the effect of electron transit time ofsaid impedance means thereby to impair the frequency correction of saidoscillator, a compensating circuit coupled to said correction circuit,means for selectively proportioning the constants of said compensatingcircuit to counteract any tendency of the phase angle of said impedanceto vary With frequency resulting from the selection of any desired oneof said plurality of different frequencies, and unicontrol means forsimultaneously operating the means for selectively proportioning` theconstants of said oscillating ,and compensating circuits, whereby saidtendency of the phase angle of said impedance to vary with frequencyresulting from the selection of the desired oscillator frequency isminimized.

3. In an ultra-high-frequency modulated-carrier signal receiver, afrequency-changing system for deriving from selected receivedmodulated-carrier signals intermediate-frequency modulated-carriersignals comprising an oscillator circuit, means for selectivelyproportioning the constants of said oscillator circuit to oscillate atany desired one of a plurality of different frequencies, afrequency-correction circuit including a vacuum tube connected tosimulate a variable impedance coupled to said oscillator circuit toadjust the frequency of said oscillator circuit to the proper value forderiving the selected intermediate-frequency signals, the phase angle ofsaid impedance incidentally tending to vary with respect to theoscillator circuit voltage with variations in frequency due to electrontransit time effects in said vacuum tube, a compensating circuit coupledto said correction circuit, and means for selectively proportioning theconstants of said compensating circuit to counteract any tendency of thephase angle of said impedance to vary with frequency resulting from theselection of any desired one of said plurality of different frequencies.

4. In an ultra-high-frequency modulated-carrier signal receiver, afrequency-changing system for deriving from selected receivedmodulated-carried signals intermediate-frequency modulated-carriersignals comprising, an oscillator circuit including a vacuum tube, meansfor selectively proportioning the constants of said oscillator circuitto oscillate at any desired one of a plurality of different frequencies,a frequencycorrection circuit including a vacuum tube connected tosimulate a variable impedance. coupled tc said oscillator circuit toadjust the frequency of said oscillator circuit to the proper valuenecessary for deriving the selected intermediatefrequency signals, thephase angles of trans-admittance of said vacuum tubes incidentallytending to vary with variations in frequency due to electron transittime effects in said vacuum tubes, a compensating circuit coupled tosaid correction circuit, and means for selectively proportioning theconstants of said compensating circuit to counteract any tendency ofsaid phase angles of transadmittance to vary with variations infrequency resulting from the selection of any desired one of saidplurality of different frequencies.

5. In an ultra-high-frequency modulated-carrier signal receiver, afrequency-changing system for deriving from selected receivedmodulated-carrier signals intermediate-frequency modulated-carriersignals comprising, an oscillator circuit, means for selectivelyproportioning the constants of said oscillator circuit to oscillate atany desired one of a plurality of different frequencies, afrequency-correction circuit including a vacuum tube coupled to saidoscillator circuit for supplying control current thereto to adjust thefrequency of said oscillator circuit to the proper value f or derivingthe selected intermediate-frequency signals, said control currentincidentally tending to vary in phase with respect to the oscillatorcircuit voltage with variations in frequency due to electron transittime eiects in said vacuum tube, and a compensating cir-v cuit coupledto said vacuum tube for controlling its electron transit time effectsand having constants selectively proportioned to counteract any tendencyof said control current to vary in phase with frequency resulting fromthe selection of any desired one of said plurality of differentfrequencies.

6. In an ultra-high-frequency modulated-carrier signal receiver, afrequency-changing system for deriving from selected receivedmodulated-carrier signals intermediate-frequency modulated-carriersignals comprising, an oscillator circuit including a vacuum tube havingan anode circuit for developing an oscillator circuit voltage, means forselectively proportioning the constants of said oscillator circuit tooscillate at any one of a plurality of different frequencies, afrequency-correction circuit coupled to said oscillator circuitincluding a vacuum tube having an anode circuit which carries a currentthat is desirably degrees out of phase with respect to said oscillatorcircuit voltage whereby said lastnamed anode circuit simulates avariable reactance to adjust the frequency of said oscillator circuit tothe proper value for deriving the selected intermediate-frequencysignals, the current in the anode circuit of said frequency-correctiontube incidentally tending to vary from said desired 90-degree phaserelation With respect to the oscillator circuit voltage with variationsin frequency due to electron transit time effects in both of said tubes,a conpensating circuit coupled to said anode circuits, and means forselectively proportioning the constants of said compensating circuits tocounteract any tendency of said anode circuit currents to vary in phasewith frequency resulting from the selection of any desired one of saidplurality of different frequencies.

JOHN A. RADO.

CERTIFICATE 0F CORRECTIQN. Y Patent No. 2,215,710. 'June 17, 19111.

JOHN A. RADO.

It is hereby certified that error appears in the printed specificationof the abovel numbered patent Ilequiring correction as follows: Page 2,firstv column, line 5'?, for "'l22l1." read '12,2l1; and second column,line` lll, lstrike out the word comprising page l1, first column,- line62', in the table, for "2- 6" read -2 -6 and that the said LettersPatent should be readwith this correction therein that the: same mayconform to the record of the case n the Patent Office.

Signed and sealed this 50th day of September, A. D. 191.11.

Henry Van Arsdale,

(Seal) Acting Commissioner .of Patents.

